1. Field of the Invention
The present invention relates to a substrate for a display panel where a drive signal is applied through a plurality of wiring electrodes drawn out from the inside to the outside of a container, and to an image forming apparatus such as a display device using the same.
2. Related Background Art
Conventionally, as display devices, the following are known: gas discharging type ones such as PDPs (plasma display panels); and electron beam irradiating type ones such as FEDs (field emission displays) where light emitting members are irradiated with electron beams. As electron-emitting devices for electron beam irradiating type displays, two kinds are known: thermionic source type ones; and cold cathode electron source type ones. The latter type includes field emission type devices (FE type devices), metal-insulator-metal devices (MIM devices), and surface conduction electron-emitting devices.
The above-mentioned surface conduction electron-emitting devices have an advantage that a number of devices can be formed over a large area since they are simple in structure and easily manufactured, and thus, various kinds of applications of the devices are under research to make full use of the advantage. The applications include those to an ion beam source, and to a display device such as an image forming apparatus. As an example, the present applicant proposed in Japanese Patent Application Laid-Open Nos. 2000-251778 and 2000-251802 an image forming apparatus in which an electron source plate where multiple electron-emitting devices are connected to wirings in a matrix and an opposing substrate having a phosphor disposed therein are laminated together to form a high vacuum container (display panel).
However, when the above-mentioned image forming apparatus is constructed in which an electron source plate where multiple electron-emitting devices are connected to wirings in a matrix and an opposing substrate having a phosphor disposed therein are laminated together to form a high vacuum container (display panel), and when the area of the image forming apparatus is made larger and the quality of the image forming apparatus is made higher, the following problems arise.
First of all, as a wiring material, thick film paste including metal and a glass material is used to satisfy required wiring resistance. However, when higher definition is tried to be achieved in order to make higher the quality of the image forming apparatus, it is necessary to make the wiring width sufficiently small in a display area. It is desirable for a high definition display device to have the wiring width of about 70 xcexcm or less in order to be sufficient for general use, though, specifically, depending on the specific purpose of using the display device.
Further, as in the case of a surface conduction electron-emitting device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-251778, when an electron source plate is used which is configured such that gaps between opposing electrode pairs (device electrodes) are disposed in parallel with column (Y) direction wirings (lower wirings) and such that electron-emitting regions are formed as lines substantially in parallel with the Y direction wirings (lower wirings), since the trajectory of emitted electrons must be controlled, it is desired that the edge height of the Y direction wirings is sufficiently high (for example, about 14 xcexcm) in the display area. The sufficient height is also necessary in order to sufficiently decrease the resistance value of the wiring as described above.
As used herein, the term xe2x80x9cdisplay areaxe2x80x9d means an orthogonal projection area of an image forming member such as a phosphor onto a wiring substrate. When a display panel is formed by disposing the above-mentioned electron source plate and a transparent substrate, having a phosphor formed therein, so as to be opposed to each other, an area on the electron source plate (wiring substrate) opposed to the phosphor is the orthogonal projection area of the image forming member (phosphor) onto the wiring substrate.
As a result of consideration of specific means for materializing formation of wirings having a minimum wiring width and a sufficient height (thickness) in order to attain both higher definition and decreased resistance of matrix wirings in the display area, we found it was preferable for the wiring formation method to be changed from conventional screen printing to photolithography using a photo paste material. More specifically, when wirings are conventionally formed using printing, since the cross section shape is a smooth hemisphere, it is difficult to materialize both a sufficient height and a high definition wiring width. As a wiring shape materializing both a narrow width and a sufficient height (thickness), a rectangle having abrupt edges is preferable. We consider that, in order to form wirings in such a shape, photolithography using a photo paste material is preferable.
However, when the thickness of the photo paste material is increased to secure an edge height of the wirings for the purpose of decreasing the wiring resistance and controlling the trajectory of electrons emitted from the electron-emitting devices, the edges of a pattern are curled (scooped) and the plate is easily subject to cracks, and thus, a problem can arise in that the airtightness is decreased (a leak path is formed) at the outer periphery of the display area where the panel is seal-bonded.
A main object of the present invention is to improve the disadvantage and to obtain a higher quality image both by attaining higher luminance and higher definition of image display devices and image forming apparatus using a wiring substrate and by materializing an airtight container capable of maintaining a vacuum atmosphere or the like.
According to an aspect of the present invention, there is provided a wiring substrate for a display panel comprising a plurality of wiring electrodes thereon, with an airtight container being formed by disposing an opposing substrate through a frame member on the surface of the substrate having the wiring electrodes, and the airtight container having an image forming member therein, in which an average angle between a cross section of the wirings and the wiring substrate in an orthogonal projection area of the image forming member onto the wiring substrate is obtuse while an average angle between a cross section of the wirings and the wiring substrate in an area where the frame member is disposed is acute.
Also, the present invention is especially effective in the case where the thickness of the wirings is 8 xcexcm or more.
Also, the present invention is especially effective in the case where atmosphere in the airtight container is depressurized atmosphere.
Also, according to the present invention, it is preferable that the width of the wirings in the orthogonal projection area of the image forming member onto the wiring substrate is narrower than the width of the wirings in the area where the frame member is disposed.
Also, according to the present invention, there is provided a manufacturing method for a wiring substrate for a display panel having a plurality of wiring electrodes thereon, with an airtight container being formed by disposing an opposing substrate through a frame member on the surface of the substrate having the wiring electrodes, and the airtight container having an image forming member therein, comprising: forming wirings in an orthogonal projection area of the image forming member onto the wiring substrate by photolithography using a photo paste; and forming wirings in an area where the frame member is disposed by pattern printing using paste ink for printing.
Also, according to still another aspect of the present invention, there is provided a manufacturing method for a wiring substrate for a display panel having a plurality of wiring electrodes thereon, with an airtight container being formed by disposing an opposing substrate through a frame member on the surface of the substrate having the wiring electrodes, and the airtight container having an image forming member therein, comprising: forming a wiring pattern in an orthogonal projection area of the image forming member onto the wiring substrate and in an area where the frame member is disposed by photolithography using a photo paste; forming an overcoat layer which disappears at a point higher than a temperature at which an organic component of the photo paste disappears and lower than a softening point of an inorganic component of the photo paste on the wiring pattern in the area where the frame member is disposed; and baking simultaneously the wiring pattern and the overcoat layer.
Also, according to still another aspect of the present invention, there is provided a manufacturing method for a wiring substrate for a display panel having a plurality of wiring electrodes thereon, with an airtight container being formed by disposing an opposing substrate through a frame member on the surface of the substrate having the wiring electrodes, and the airtight container having an image forming member therein, comprising: forming first wirings in an orthogonal projection area of the image forming member onto the wiring substrate and in an area where the frame member is disposed by photolithography using a photo paste; and forming second wirings on the first wirings in the area where the frame member is disposed by pattern printing using paste ink for printing.
Also, according to the present invention, there is provided an image display device using a wiring substrate according to any one of the above-mentioned aspects of the invention.
According to the present invention, when a desired wiring height is secured to decrease the wiring resistance and a structure of the present invention is used as wirings for supplying signals to electron-emitting devices in the display area, the trajectory of emitted electrons can be satisfactorily controlled. In a seal-bonding portion outside the display area, a wiring substrate free from wiring edge curls and side cracks can be materialized.
Further, by using such a wiring substrate, an image forming apparatus such as an image display device having improved light emission efficiency and having airtightness and reliability which are high enough to maintain a vacuum or the like can be materialized.